Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2016	Jun. 30, 2017
Goodwill [Roll Forward]
Beginning Balance		$ 21,024
Business Acquisitions		(158)
Business Divestitures		(1,270)
Currency Translation and Other		23
Ending Balance		19,619
Building Efficiency Systems and Service North America
Goodwill [Roll Forward]
Business Divestitures	$ (3)
Power Solutions
Goodwill [Roll Forward]
Beginning Balance		1,086
Business Acquisitions		0
Business Divestitures		0
Currency Translation and Other		0
Ending Balance		1,086
Building Technologies & Solutions [Member] \| Building Technologies & Solutions Tyco [Member]
Goodwill [Roll Forward]
Beginning Balance		16,308
Business Acquisitions		(160)
Business Divestitures		(1,270)
Currency Translation and Other		40
Ending Balance		14,918
Building Efficiency \| Building Efficiency Systems and Service North America
Goodwill [Roll Forward]
Beginning Balance		975
Business Acquisitions		0
Business Divestitures		0
Currency Translation and Other		0
Ending Balance		975
Building Efficiency \| Building Efficiency Products North America [Member]
Goodwill [Roll Forward]
Beginning Balance		1,697
Business Acquisitions		1
Business Divestitures		0
Currency Translation and Other		2
Ending Balance		1,700
Building Efficiency \| Building Efficiency Asia
Goodwill [Roll Forward]
Beginning Balance		657
Business Acquisitions		0
Business Divestitures		0
Currency Translation and Other		(23)
Ending Balance		634
Building Efficiency \| Building Efficiency Rest of World [Member]
Goodwill [Roll Forward]
Beginning Balance		301
Business Acquisitions		1
Business Divestitures		0
Currency Translation and Other		4
Ending Balance		$ 306

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

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